them.
Old diseases can return if the conditions change to favor their reemergence. For example, the increased use of antibiotics in hospital settings with inadequate stewardship has led to known pathogens, such as Clostridium difficile, Klebsiella pneumoniae, Streptococcus pneumoniae, and methicillin-resistant Staphylococcus aureus (MRSA), acquiring new antibiotic-resistance traits that now challenge measures to control their spread. Unfortunately, noncompliance with hygiene practices by health care workers promotes the spread of these bacteria among susceptible hosts.
As another example, tuberculosis made a comeback in developed countries, such as the United States and Europe during the 1990s. Its reemergence was due to several causes. One was the dismantling of the preventive infrastructure that had been developed in the 1950s to contain the spread of this insidious disease. Another was the presence of unprecedentedly large populations of highly susceptible individuals in crowded settings, such as prisons and homeless shelters. Further complicating matters were the emergence of other illnesses, such as AIDS, that suppress the immune system of afflicted individuals and the development of resistance to the traditional anti-tuberculosis drugs, which had not been updated or improved since their original introduction because no one thought tuberculosis would return.
Foodborne and Waterborne Infections
Many foodborne and waterborne infections fit into the category of emerging or reemerging infectious diseases. We treat this subject as a separate category because of its unique impact on the public perception of disease risks. Ironically, as food and water supplies have become cleaner, the public’s concern about their integrity has increased rather than decreased. A review of news articles from the past few years makes this quite evident. The integrity of the food and water supplies is a nonnegotiable issue as far as the public is concerned.
From the 1960s through the 1980s, the public’s main concern about the food supply was pesticide residues and other chemical adulterants that might cause cancer. This problem has been largely solved by more stringent regulations and testing, which limit the amount of pesticide residues and other harmful chemicals that might be found in food sold for human consumption. More recently, concern has arisen about another hazard that had been around all along but had not been perceived as a threat: foodborne bacterial diseases.
The catalyst for the abrupt swing in public concern regarding food safety was Escherichia coli O157:H7, a type of E. coli that can cause kidney failure and death, especially in children. Widespread media attention was first drawn to this problem in 1993, when an outbreak of disease was caused by undercooked, contaminated hamburger meat dispensed by an American fast-food chain. Although there had been prior outbreaks in the previous decade, many in the beef and fast-food industries and most of the general public had never heard of E. coli up to this point. In total, this outbreak involved 732 cases, including 4 deaths, from 73 restaurants in a number of western states before the source of the outbreak was identified and the contaminated meat was recalled. Since then, there have been many more cases of E. coli O157:H7 infections spread by undercooked meat, radish sprouts, lettuce, spinach, and even apple juice. The apple juice incident, during which 65 cases with 1 death were reported, nearly bankrupted the company that had produced the contaminated juice, which had not been pasteurized. The lesson that juice was not exempt from bacterial contamination was learned very quickly by the industry, and it is now rare to see unpasteurized juices in supermarkets.
Earlier in the 20th century, before the advent of centralized food processing and distribution, foodborne disease outbreaks tended to be confined to church socials, family gatherings, or business-sponsored employee picnics (Box 1-2). As the food industry became more centralized, however, a different pattern of foodborne disease emerged: the multistate (or even multicountry) outbreak of foodborne disease derived from a single source. The nature of foodborne outbreaks has changed considerably from the days of the church social outbreaks, and the effect on the public has been dramatic. In the case of the E. coli O157:H7 outbreak described above, a single processing plant was the source. Contaminated radish sprouts caused another outbreak of E. coli O157:H7 in Japanese schoolchildren. The seeds used by the Japanese sprouting companies came from a single source in the northwestern United States, where the initial contamination event probably occurred. In 2006, E. coli O157:H7-contaminated spinach grown in California and used by consumers in spinach salads was spread throughout the United States. In 2009, E. coli O157:H7 showed up yet again, this time in refrigerated cookie dough sold throughout the United States.
Box 1-2.
Bioterrorism Hits Oregon Salad Bars
In 1984, a large outbreak of salmonellosis involving at least 750 people occurred in The Dalles, the county seat of Wasco County in Oregon. At the time, a religious commune was at odds with local residents over land-use restrictions placed on the commune in an attempt by the townspeople to eliminate it. Members of the commune felt that the outcome of an upcoming election was critical to their future ability to grow. In an apparent attempt to disrupt the election, commune members planned to cause an outbreak of salmonellosis that would keep people home from the polls. The outbreak was a trial run to determine the best way to create the most havoc. At least 10 restaurants were involved, with the salad bar being the main site of intentional contamination. Contamination attempts were also made at local grocery stores, but the restaurant salad bars were the most effective source of disease. Unfortunately for commune members, their trial run was too successful and attracted the attention of the Public Health Department and the police.
Even so, it took nearly a year to trace the epidemic source and to suspect intentional contamination. Such events are fortunately quite rare, so intentional contamination was not even considered at first as a possible explanation for the outbreak. Careful questioning of the victims led investigators to deduce that salad bars had been the main source of the outbreak. Further interrogation of commune members by police and FBI agents revealed that the commune members had been the perpetrators of the outbreak. The commune had its own laboratory, where the strain of Salmonella enterica serovar Typhimurium was grown and prepared for inoculation of the salad bars. Commune members had apparently gotten the strain by ordering it from the American Type Culture Collection (ATCC), a widely respected repository of bacterial strains that distributes strains to scientific laboratories for a modest fee. Nearly 2 years after the outbreak, two commune members were sentenced to 1 to 2 years in prison for conspiring to tamper with consumer products. An earlier episode of product tampering involving introduction of cyanide into Tylenol capsules had been responsible for a rash of antitampering legislation. These antitampering laws were used to prosecute the commune members. As a precaution against misuse of its cultures, the ATCC has tightened restrictions on obtaining certain bacterial stocks.
Source:
Török TJ, Tauxe RV, Wise RP, Livengood JR, Sokolow R, Mauvais S, Birkness KA, Skeels MR, Horan JM, Foster LR. 1997. A large community outbreak of salmonellosis caused by intentional contamination of restaurant salad bars. JAMA 278:389–395.[PubMed][CrossRef]
Similar to foodborne diseases, outbreaks of waterborne disease continue to occur, despite advances in water management and sanitation; however, they tend to be more localized in nature. Most of the waterborne outbreaks that have made the news lately were caused by aging pipes and water treatment plants or by mammal and bird fecal material in water reservoirs. Over half of all waterborne illnesses in the United States in recent years have been associated with contamination of drinking water with Legionella, a Gram-negative bacterium commonly found in soil and aquatic environments. Other microbes associated with waterborne outbreaks are E. coli and Campylobacter bacteria and the parasites Giardia and Cryptosporidium. The media picked up on this contamination problem, as was seen on a cover of Time magazine (August 3, 1998) showing E. coli cascading out of a kitchen tap. The event that stimulated this particular
